Performance of Iterative Reconstruction in Image Space Algorithm in Combination with Automatic Tube Current Modulation Compared to Filtered Back Projection in Brain CT Scan

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Abstract

Background:

High-quality images with minimum radiation dose are considered a challenge in Computed Tomography (CT) scans.

Objective:

The current study aimed to assess the efficacy of the Iterative Reconstruction in Image Space (IRIS) algorithm combined with Automatic Tube Current Modulation (ATCM) compared to Filtered Back Projection (FBP) in brain CT scans.

Material and Methods:

In this cross-sectional study, 200 patients underwent to brain CT scan, and images were then reconstructed using both FBP and IRIS. The CT Number (CTN), noise, and Signal-to-Noise Ratio (SNR) were computed for different tissues from CT images. The performance of two algorithms under different exposure conditions was evaluated using a water phantom. Two experienced radiologists assessed the image quality. Volume CT Dose Index (CTDI _vol) and Dose Length Product (DLP) were recorded for each scan.

Results:

FBP reconstruction exhibited higher noise and lower SNR compared to IRIS, both with and without ATCM. Noise levels significantly increased for FBP combined with ATCM. Subjective analysis showed higher performance for IRIS without ATCM compared to other approaches. The mean CTDI _vol with and without ATCM was 20.04±3.33 and 36.37±4.65 mGy, respectively. In the phantom study, the noise with IRIS remained lower than that with FBP even with a 42% dose reduction.

Conclusion:

IRIS algorithm can preserve the image quality when radiation dose is significantly reduced by ATCM in brain CT scan. Implementation of IRIS combined with ATCM is recommended for brain CT examinations.

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Most cited references 25

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Iterative reconstruction in head CT: image quality of routine and low-dose protocols in comparison with standard filtered back-projection.

A. Korn, M Fenchel, B Bender … (2012)

IR has recently demonstrated its capacity to reduce noise and permit dose reduction in abdominal and thoracic CT applications. The purpose of our study was to assess the potential benefit of IR in head CT by comparing objective and subjective image quality with standard FBP at various dose levels. Ninety consecutive patients were randomly assigned to undergo nonenhanced and contrast-enhanced head CT at a standard dose (320 mAs; CTDI, 60.1) or 15% (275 mAs; CTDI, 51.8) and 30% (225 mAs; CTDI, 42.3) dose reduction. All acquisitions were reconstructed with IR in image space, and FBP and images were assessed in terms of quantitative and qualitative IQ. Compared with FBP, IR resulted in lower image noise (P ≤ .02), higher CNR (P ≤ .03), and improved subjective image quality (P ≤ .002) at all dose levels. While degradation of objective and subjective IQ at 15% dose reduction was fully compensated by IR (CNR, 1.98 ± 0.4 at 320 mAs with FBP versus 2.05 ± 0.4 at 275 mAs with IR; IQ, 1.8 versus 1.7), IQ was considerably poorer at 70% standard dose despite using the iterative approach (CNR, 1.98 ± 0.3 at 320 mAs with FBP versus 1.85 ± 0.4 at 225 mAs with IR, P = .18; IQ, 1.8 versus 2.2, P = .03). Linear regression analysis of CNR against tube current suggests that standard CNR may be obtained until approximately 20.4% dose reduction when IR is used. Compared with conventional FBP, IR of head CT is associated with significant improvement of objective and subjective IQ and may allow dose reductions in the range of 20% without compromising standard image quality.

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Image reconstruction: Part 1 – understanding filtered back projection, noise and image acquisition

R. Schofield, L. King, U Tayal … (2019)

Image reconstruction is an increasingly complex field in CT. Iterative Reconstruction (IR) is at present an adjunct to standard Filtered Back Projection (FBP) reconstruction, but could become a replacement for it. Due to its potential for scanning at lower radiation doses, IR has received a lot of attention in the medical literature and all vendors offer commercial solutions. Its use in cardiovascular CT has been driven in part due to concerns about radiation dose and image quality. This paper is the first manuscript of a pair. It aims to review the basic principles of CT scanning, to describe image reconstruction using Filtered Back Projection, and to identify the physical processes that contribute to image noise which IR may be able to compensate for. The aim is to enable cardiovascular imagers to understand what happens to the raw data prior to the reconstruction process so they may have a better appreciation of the strengths and weaknesses of the various reconstruction techniques available. The second manuscript of this pair will discuss the various vendor permutations of IR in more detail, including the most recent machine learning based offerings, and critically appraise the current clinical research available on the various IR techniques used in cardiovascular CT.

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80-kVp CT Using Iterative Reconstruction in Image Space Algorithm for the Detection of Hypervascular Hepatocellular Carcinoma: Phantom and Initial Clinical Experience

Saebeom Hur, Jeong Min Lee, Soo Jin Kim … (2012)

Objective To investigate whether the low-tube-voltage (80-kVp), intermediate-tube-current (340-mAs) MDCT using the Iterative Reconstruction in Image Space (IRIS) algorithm improves lesion-to-liver contrast at reduced radiation dosage while maintaining acceptable image noise in the detection of hepatocellular carcinomas (HCC) in thin (mean body mass index, 24 ± 0.4 kg/m2) adults. Subjects and Methods A phantom simulating the liver with HCC was scanned at 50-400 mAs for 80, 100, 120 and 140-kVp. In addition, fifty patients with HCC who underwent multiphasic liver CT using dual-energy (80-kVp and 140-kVp) arterial scans were enrolled. Virtual 120-kVP scans (protocol A) and 80-kVp scans (protocol B) of the late arterial phase were reconstructed with filtered back-projection (FBP), while corresponding 80-kVp scans were reconstructed with IRIS (protocol C). Contrast-to-noise ratio (CNR) of HCCs and abdominal organs were assessed quantitatively, whereas lesion conspicuity, image noise, and overall image quality were assessed qualitatively. Results IRIS effectively reduced image noise, and yielded 29% higher CNR than the FBP at equivalent tube voltage and current in the phantom study. In the quantitative patient study, protocol C helped improve CNR by 51% and 172% than protocols A and B (p < 0.001), respectively, at equivalent radiation dosage. In the qualitative study, protocol C acquired the highest score for lesion conspicuity albeit with an inferior score to protocol A for overall image quality (p < 0.001). Mean effective dose was 2.63-mSv with protocol A and 1.12-mSv with protocols B and C. Conclusion CT using the low-tube-voltage, intermediate-tube-current and IRIS help improve lesion-to-liver CNR of HCC in thin adults during the arterial phase at a lower radiation dose when compared with the standard technique using 120-kVp and FBP.

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Author and article information

Journal

Journal ID (nlm-ta): J Biomed Phys Eng

Journal ID (iso-abbrev): J Biomed Phys Eng

Title: Journal of Biomedical Physics & Engineering

Publisher: Shiraz University of Medical Sciences (Iran )

ISSN (Electronic): 2251-7200

Publication date Collection: August 2024

Publication date (Electronic): 01 August 2024

Volume: 14

Issue: 4

Pages: 379-388

Affiliations

[1 ] Department of Radiology Technology, School of Paramedicine, Hamadan University of Medical Sciences, Hamadan, Iran

[2 ] Department of Radiology, School of Medicine, Hamadan University of Medical Sciences, Hamadan, Iran

Author notes

*Corresponding author: Salman Jafari, Department of Radiology Technology, School of Paramedicine, Hamadan University of Medical Sciences, Hamadan, Iran

E-mail: sa.jafari@ 123456umsha.ac.ir

Article

Publisher ID: JBPE-14-4

DOI: 10.31661/jbpe.v0i0.2404-1741

PMC ID: 11336050

SO-VID: 02619ae2-bf41-41e2-a8f8-2b4022edd642

License:

This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 Unported License, ( http://creativecommons.org/licenses/by-nc/4.0/ ) which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited non-commercially.

Performance of Iterative Reconstruction in Image Space Algorithm in Combination with Automatic Tube Current Modulation Compared to Filtered Back Projection in Brain CT Scan

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Abstract

Background:

Objective:

Material and Methods:

Results:

Conclusion:

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The Dynamic Brain

Most cited references 25

Iterative reconstruction in head CT: image quality of routine and low-dose protocols in comparison with standard filtered back-projection.

Image reconstruction: Part 1 – understanding filtered back projection, noise and image acquisition

80-kVp CT Using Iterative Reconstruction in Image Space Algorithm for the Detection of Hypervascular Hepatocellular Carcinoma: Phantom and Initial Clinical Experience

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